Computer monitors can have cathode ray tubes (CRT), liquid crystal displays (LCD) plasma screens, projections screens or flat panels as the screen that emits light according to electrical signals from a computer. The computer generates a standard set of instructions that produces electrical signals that the monitor uses to produce images on the screen.
However, monitors from different manufacturers produce different intensity levels of color on the screen for the same set of signals. In this respect, the same image viewed on monitors from different manufacturers or using different manufacturing technologies may appear different to a user because of different display characteristics such as primaries, optical transfer function, and white point. In order to overcome these differences, the monitors may be calibrated so that the color differences between monitors may be reduced.
This need for calibration is especially important for LCD screens. Often times LCD screens from different manufacturers or employing different display technologies will be used in the same product line. To ensure that the images are viewed consistently among monitors of the same product line, each LCD screen is calibrated.
Measurement tests are performed on the screen of the monitor to determine calibration settings. When each monitor is manufactured, the calibration settings are used to adjust how the monitor produces colors in order to generate consistent images. The calibration settings can also be applied in the computer system to the electrical signals that are sent to the monitor when the monitor is in use.
The calibration settings are found using a calibration system having a light sensor and a method to generate the calibration parameters from the values recorded by the sensor. A computer generates color test images on the monitor that are measured by the light sensor facing the screen. The light sensor measures the color parameters of the test images. The measurements are communicated back to the computer which generates the calibration settings therefrom.
The measurements can be a color parameter such as either tristimulus values in the form of (X, Y and Z), chromaticity (x,y) and luminance (Y(Cd/m2)), or CIELAB values (L*a*b*). By measuring the color parameter for a number of colors, it is possible to determine calibration settings that are used to calibrate the monitor to accurately and consistently reproduce colors according to a reference calibration, which is usually referred to as target calibration.
In prior art methods, the number of multiple light measurements is fixed and set by the operator prior to performing the measurement. Thus, the computer takes multiple measurements for all the colors irrespective of whether the color is lighter or darker. In other words, multiple measurements are taken for the light colors even though they are not needed. By performing multiple measurements on each of the colors, the time to measure the color parameter is longer than what is really needed.
The present invention addresses the above-mentioned inefficiencies in measuring color parameter values by providing a system and method that determines the number of measurements to be performed. The system of the present invention only performs extra color measurements when they are needed, thereby avoiding extra measurements and thereby greatly increasing measurement speed.